Plasma enhanced chemical vapor deposition of silicon thin films and materials' characterization

• Κύριος συγγραφέας: Αλεξίου, Ιωάννης
• Άλλοι συγγραφείς: Ματαράς, Δημήτριος
• Μορφή: Thesis
• Γλώσσα: English
• Έκδοση: 2018
• Θέματα: Dust particles; Microcrystalline hydrognated silicon; PECVD; Μικροκρυσταλλικό υδρογονωμένο πυρίτιο; Χημική εναπόθεση ατμών υποβοηθούμενη με πλάσμα; 621.381 045

Amorphous (a-Si:H) and microcrystalline (μc-Si:H) hydrogenated silicon, have attracted particular attention during the last decades due to their application in optoelectronic devices (transistors, thin film solar cells, TFTs etc.). These materials are produced via Plasma Enhanced Chemical Vapor Deposition (PECVD) technique through capacitively coupled (CCP) SiH4/H2 glow discharges. The main advantages of this technique are the possibility to deposit device grade materials at low temperatures and over large areas (> 1 m2). On the other hand, the main disadvantages of the method are the rather low deposition rate and the dust formation in the gas phase, which can under certain conditions affect the reproducibility of the process and deteriorate the film properties. Thus, the aim of the present thesis is to study the effect of several SiH4/H2 discharge parameters on the dust formation, deposition rate and film properties. The main target is the determination of the basic plasma properties that fulfill the following requirements: (a) relatively high μc-Si:H film growth rate, (b) film optical properties and crystallinity, suitable for application in photovoltaics and (c) the control of particles formation. In order to achieve these goals several depositions were performed and analyzed with the aid of plasma diagnostics, surface characterization methods and gas phase theoretical analysis. According to the results, the variation of several discharge parameters led to the deposition of crystalline materials at relatively high growth rates. Furthermore, the several stages of dust particles formation were monitored via the self-bias voltage (Vdc) and optical emission spectroscopy (OES) measurements. Discharge parameters as total gas pressure and temperature was found that strongly affect the growth of dust particles. Finally, the pulsed plasma modulation method was proposed as a method that can be used in order to suppress or control the dust particle growth.